Indium Complexes of Fluorinated Dialkoxy-Diimino Salen-like Ligands for Ring-Opening Polymerization of racemic Lactide: How does Indium Compare to Aluminum? - Université de Rennes Accéder directement au contenu
Article Dans Une Revue Organometallics Année : 2011

Indium Complexes of Fluorinated Dialkoxy-Diimino Salen-like Ligands for Ring-Opening Polymerization of racemic Lactide: How does Indium Compare to Aluminum?

Résumé

The reaction between InCl3 and {ONEtNO}K2 (1a), prepared from (CF3)2(OH)CCH2C(CH3)═N-R-N═C(CH3)CH2C(OH)(CF3)2 ({ONEtNO}H2, R = C2H4 (a); {ONCyNO}H2, R = rac-1,2-cyclohexylene (b)) and PhCH2K, gave {ONEtNO}InCl (2a). The reaction between InCl3 and 3 equiv of MeLi led to a mixture of [InMe3] and Li[InMe4], which upon further treatment with {ONRNO}H2 proligands gave the ate complexes [{ONRNO}Li]InMe2 (4a,b); the methyl complex {ONEtNO}InMe (3a) was also isolated from this reaction. Hydrocarbyl complexes {ONRNO}In(CH2SiMe3) (5a,b) were prepared cleanly from the 1:1 reactions between In(CH2SiMe3)3 and {ONRNO}H2. The solid-state molecular structures of mononuclear 2a, 3a, 4b, and 5b and of [(1a)2-(μ-H2O)]n, a distorted cubane-like core made up of four potassium atoms and two ligands, were determined. Compounds 5a,b are moderately active initiators/catalysts for the ring-opening polymerization of rac-lactide, giving polymers with controlled molecular weights and narrow polydispersities, especially in the presence of added isopropyl alcohol (1-10 equiv) as exogenous initiator. Isotactic-enriched (Pm = 0.62-0.69) PLAs were obtained from 5a, while 5b gave atactic materials. The heterobimetallic compounds 4a,b are also active and afforded slightly heterotactic-enriched PLAs (Pr = 0.57-0.62), but with broader polydispersities. Those results allowed us to discuss the initiation mechanisms according to the constitution of the systems (alkyl vs alkyl/iPrOH) and also stereoselective abilities as a function of the nature (In vs Al) and coordination environment (κ4-ONNO vs. κ2-NN) of the metal center.

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Catalyse
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Dates et versions

hal-00872416 , version 1 (12-10-2013)

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Mickaël Normand, Evgeny Kirillov, Thierry Roisnel, Jean-François Carpentier. Indium Complexes of Fluorinated Dialkoxy-Diimino Salen-like Ligands for Ring-Opening Polymerization of racemic Lactide: How does Indium Compare to Aluminum?. Organometallics, 2011, 31 (4), pp.1448-1457. ⟨10.1021/om200906e⟩. ⟨hal-00872416⟩
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